1. Field of the Invention
The present invention relates to a headrest for a vehicle seat, and, in particular, to such headrest of the type that the headrest proper can be directly operated so as to simply adjust its longitudinal positions relative to a seat back, that is, the distance between the occupant's head and itself.
2. Description of the Prior Art
Conventionally, as headrests of this kind, there have been well known three types of headrests. A first one of them is provided with a gear mechanism located between a headrest proper and a rotary support member and maintained in constant mesh. In this headrest, such gear mechanism can be rotatively operated by a knob attached to the headrest proper so as to adjust the rotational angle of the headrest proper. A second one is equipped with a lock mechanism in its rotary support member which can be unlocked by means of external button operation to rotate a headrest proper for its angular adjustment. A third one includes in the rotary support portion of the headrest proper a rotary mechanism having a friction action so that the headrest proper can be directly operated or rotated.
In the former two conventional headrests, it is true that the respective rotary support portions of their respective headrests proper are enough to bear the loads of the occupant's head in case of collisions or the like because their teeth are maintained meshed with one another in the first example and the lock mechanism maintains the rotary support portion in its locked position. However, when adjusting the angles of rotation of the respective headrests proper, in both the forward and rearward directions, it is necessary to operate the knob rotatively or to operate a lock release button, which delays the angular adjustments, that is, quick adjustments are impossible.
On the other hand, in the last-mentioned conventional headrest, since the rotary support postion of the headrest proper is maintained in its engaged condition due to friction action, the adjustment of angle of rotation of the headrest proper can be performed by pushing it directly. However, when a grater load due to the shocks of the occupant's head occurring in case of collisions or the like is applied to the headrest proper, it may be rotated unnecessarily, which makes it impossible to hold the occupant's head positively upright. If the friction of the rotary support portion is increased in order to prevent such unnecessary rotation, then the adjustment of the angle of rotation cannot be carried out smoothly.
There is known an improved headrest which is disclosed in Japanese Utility Model No. 52863 of 1982, aimed at eliminating the drawbacks in the above-mentioned prior art headrests. However, since the improved headrest is constructed such that it can be adjusted forwardly or rearwardly by rotating itself, its surface in contact with the occupant's head may be faced upwardly or downwardly according to the forward or rearward adjustment thereof, resulting in troublesome or inconvenient use thereof.